1. Field of the Invention
The present invention relates to a side support device for use with a seat in a vehicle which is capable of controlling the movement of a side support of the vehicle seat according to the operating conditions of the vehicle to prevent an occupant of the seat from losing his or her position.
2. Description of the Prior Art
When a vehicle goes around a curve, an occupant of a vehicle seat feels given an acceleration in a lateral direction to get the occupant down, due to generation of centrifugal force. As a result of this, the occupant is forced to lose his or her sitting position, which makes it difficult for the occupant to support his or her predetermined sitting position and also hurts the comfortable feel to the occupant of the ride to a great extent. Especially, in case of a driver of the vehicle, to lose his or her sitting posture may be an obstacle to the driving operation of the driver, which is dangerous.
To avoid this problem, conventionally, there have been proposed side support devices which are constructed to prevent the seat occupant from losing his or her sitting position to thereby support the user's predetermined comfortable sitting position, and such side support devices have been mounted to a driver's seat and the like.
For example, in one of the above-mentioned prior art side support devices, there is provided a side support which is disposed in a seat back of the seat. This side support is constructed such that it presses against and holds between the upper body of the occupant from both sides thereof to control the movements of the occupant's upper body so as to be able to support the predetermined sitting posture of the occupant by force. However, if the side support always supports the occupant's upper body from both sides thereof, then the occupant is deprived of the freedom of the movements of the upper body, which hurts the riding comfort of the occupant and makes the occupant uncomfortable and also makes the occupant tired. For this reason, the side support is normally positioned at an open position in which the occupant is not held and, only in case of need, it can be moved to a closed position for holding the occupant.
Also, as the side support device adapted to control the movements of the side support, there is widely known a device of a type that employs the lateral acceleration (acceleration in a lateral direction) as a parameter. The lateral acceleration can be detected directly by an acceleration sensor (for example, Japanese Utility Model Publication No. 97633 of 1985), or it may be found from the speed of a vehicle, curvature of a curve and the like (for example, Japanese Patent Publication (Tokkai) No. 67638 of 1986). In this type of side support device, the side support is moved to its closed position when the acceleration (namely, the lateral acceleration) exceeds a reference value. The parameter is not always limited to the acceleration. For example, in Japanese Utility Model Publication No. 97634 of 1985, the vehicle speed and the turning angle of a steering wheel are used as the parameter and, in Japanese Patent Publication (Tokkai) No. 197436 of 1985, the curvature of a curve and the vehicle speed are employed.
The parameter such as the lateral acceleration or the like is detected by a sensor and the detected value thereof is transmitted to a microcomputer, in which the value is compared with a reference value. When it is found that the detected value exceeds the reference value, then an output signal is transmitted from the microcomputer to a motor for driving the side support and, responsive to the output signal, the motor is rotated (in a forward direction) to thereby drive the side support to its closed position. When located at the closed position, the side support presses against and holds the upper body of the occupant therebetween to thereby prevent the occupant from losing his or her sitting posture. After then, for example, in a given time after the detected value goes below the reference value, an output signal is transmitted from the microcomputer to the motor. Responsive to this, the motor is rotated (in a reverse direction) to thereby move the side support to its open position, releasing the upper body of the occupant.
As described above, in the well known side support devices according the prior art, the parameters such as the lateral acceleration and the like are detected by use of the sensor and the detected value thereof is processed by the microcomputer. However, both the sensor and microcomputer are comparatively expensive and, therefore, the side support device employing such a microcomputer and sensor cannot be supplied at low prices.
Also, while the motor and microcomputer are disposed in the seat, the sensor is arranged in the body of the vehicle, not in the seat. For this reason, a wiring between the sensor and microcomputer must be provided externally of the seat, which makes the structure of the device complicated and thus the device cannot be mounted with ease.